Add state_key and rejection_reason to events (#11792)

... and start populating them for new events

synapse/storage/schema/__init__.py

@@ -56,13 +56,15 @@ Changes in SCHEMA_VERSION = 67:
 
 Changes in SCHEMA_VERSION = 68:
     - event_reference_hashes is no longer read.
+    - `events` has `state_key` and `rejection_reason` columns, which are populated for
+      new events.
 """
 
 
 SCHEMA_COMPAT_VERSION = (
-    # we have removed the public_room_list_stream table, so are now incompatible with
-    # synapses wth SCHEMA_VERSION < 63.
-    63
+    # we now have `state_key` columns in both `events` and `state_events`, so
+    # now incompatible with synapses wth SCHEMA_VERSION < 66.
+    66
 )
 """Limit on how far the synapse codebase can be rolled back without breaking db compat
 

synapse/storage/schema/main/delta/68/01event_columns.sql

@@ -0,0 +1,26 @@
+/* Copyright 2022 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- Add new colums to the `events` table which will (one day) make the `state_events`
+-- and `rejections` tables redundant.
+
+ALTER TABLE events
+  -- if this event is a state event, its state key
+  ADD COLUMN state_key TEXT DEFAULT NULL;
+
+
+ALTER TABLE events
+  -- if this event was rejected, the reason it was rejected.
+  ADD COLUMN rejection_reason TEXT DEFAULT NULL;